An efficient hydrogen production process using solar thermo-electrochemical water-splitting cycle and its techno-economic analyses and multi-objective optimization

A conceptual solar thermo-electrochemical water-splitting system is developed for producing green hydrogen and electricity. The system consists of a solar power tower and thermal energy storage subsystem, a four-step Cu-Cl thermo-electrochemical water-splitting cycle, supercritical CO2 Brayton cycle, and waste heat recovery unit with an organic Rankine cycle. The system is simulated in Aspen Plus with the mathematical models of the heliostat fields and electrolyzer written in the Fortran language and embedded. The performance of the proposed system is evaluated and optimized based on energy, exergy, techno-economic analysis, and sustainability assessment. The tradeoff between maximum exergy efficiency, minimum total annual cost (TAC), and minimum levelized cost of hydrogen (LCOH) is conducted by multi-objective optimization, which is implemented based on the non-dominated sorting genetic algorithm-II and the interaction between Aspen Plus and MATLAB software. The Pareto solutions indicate that the optimal exergy efficiency, TAC, and LCOH are 48.72 %, 50.96 M$/year, and 1.28 $/kg, respectively, and the LCOH is 36 % lower than that reported in the literature.